Normal State Properties and Upper Critical Magnetic Field in Three-dimensional Polycrystalline Niobium Films

2021 ◽  
Author(s):  
Xiu-Zhi Duan ◽  
Zhi-Hao He
Keyword(s):  
Magnetic Field ◽  
Normal State ◽  
Three Dimensional ◽  
Critical Magnetic Field ◽  
Upper Critical Magnetic Field ◽  
Normal State Properties

scholarly journals Evaluating Superconductors through Current Induced Depairing

2019 ◽  
Vol 4 (2) ◽  
pp. 54
Author(s):  
Milind N. Kunchur
Keyword(s):  
Magnetic Field ◽  
Current Density ◽  
Normal State ◽  
Critical Magnetic Field ◽  
Point Of View ◽  
Measured Parameter ◽  
Practical Applications ◽  
Upper Critical Magnetic Field ◽  
Equal Importance ◽  
Normal States

The phenomenon of superconductivity occurs in the phase space of three principal parameters: temperature T, magnetic field B, and current density j. The critical temperature T c is one of the first parameters that is measured and in a certain way defines the superconductor. From the practical applications point of view, of equal importance is the upper critical magnetic field B c 2 and conventional critical current density j c (above which the system begins to show resistance without entering the normal state). However, a seldom-measured parameter, the depairing current density j d , holds the same fundamental importance as T c and B c 2 , in that it defines a boundary between the superconducting and normal states. A study of j d sheds unique light on other important characteristics of the superconducting state such as the superfluid density and the nature of the normal state below T c , information that can play a key role in better understanding newly-discovered superconducting materials. From a measurement perspective, the extremely high values of j d make it difficult to measure, which is the reason why it is seldom measured. Here, we will review the fundamentals of current-induced depairing and the fast-pulsed current technique that facilitates its measurement and discuss the results of its application to the topological-insulator/chalcogenide interfacial superconducting system.

FLUCTUATION EFFECTS NEAR THE UPPER CRITICAL MAGNETIC FIELD IN HIGH-TcSUPERCONDUCTORS

1992 ◽  
Vol 06 (08) ◽  
pp. 1209-1218 ◽  
Author(s):  
S.A. KTITOROV ◽  
YU. V. PETROV ◽  
B.N. SHALAEV ◽  
V.S. SHERSTINOV
Keyword(s):  
Magnetic Field ◽  
Field Theory ◽  
Order Parameter ◽  
Three Dimensional ◽  
Critical Magnetic Field ◽  
Landau Levels ◽  
Flux Quantum ◽  
Upper Critical Magnetic Field ◽  
Lattice Effects ◽  
Fluctuation Effects

The effect of fluctuations on the thermodynamics of high-Tc superconductors near the upper critical magnetic field is studied. Lattice effects and, in particular, Harper broadening and splitting of the Landau levels are shown to reduce the problem in consideration to some renormalizable field theory with q-component, a complex order parameter. The number q is determined by the relation Φ/Φ0=p/q, where Φ is the magnetic flux through the plaquette, p and q are integral numbers, Φ0=hc/e is the Onsager flux quantum. A critical behaviour of the model for small values q=1, 2, 3, 4 is analysed and the phase transition is shown to be of the second order. A crossover from one- to three-dimensional fluctuation regime is analysed. The case of q→∞ is qualitatively discussed too.

STABLE hc/e VORTICES IN SUPERCONDUCTORS WITH SPIN-CHARGE SEPARATION

1992 ◽  
Vol 06 (05n06) ◽  
pp. 509-526
Author(s):  
Subir Sachdev
Keyword(s):  
Magnetic Field ◽  
Magnetic Flux ◽  
Normal State ◽  
Phenomenological Model ◽  
Charge Separation ◽  
Cuprate Superconductors ◽  
Superconducting Phase ◽  
Low Energy ◽  
Large N ◽  
Normal State Properties

A phenomenological model, F, of the superconducting phase of systems with spin-charge separation and antiferromagnetically induced pairing is studied. Above Hc1, magnetic flux can always pierce the superconductor in vortices with flux hc/2e, but regimes are found in which vortices with flux hc/e are preferred. Little-Park and other experiments, which examine periodicities with a varying magnetic field, always observe a period of hc/2e. The low energy properties of a symplectic large-N expansion of a model of the cuprate superconductors are argued to be well described by F. This analysis and some normal state properties of the cuprates suggest that hc/e vortices should be stable at the lowest dopings away from the insulating state at which superconductivity first occurs.

Upper Critical Magnetic Field of the Heavy-Fermion Superconductor UBe13

1985 ◽  
Vol 54 (5) ◽  
pp. 477-480 ◽  
Author(s):  
M. B. Maple ◽  
J. W. Chen ◽  
S. E. Lambert ◽  
Z. Fisk ◽  
J. L. Smith ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Heavy Fermion ◽  
Critical Magnetic Field ◽  
Upper Critical Magnetic Field ◽  
Heavy Fermion Superconductor

scholarly journals Theoretical Study of Upper Critical Magnetic Field (HC2) in Multiband Iron Based Superconductors

2016 ◽  
Vol 2016 ◽  
pp. 1-10 ◽  
Author(s):  
Tsadik Kidanemariam ◽  
Gebregziabher Kahsay
Keyword(s):  
Magnetic Field ◽  
Phase Diagrams ◽  
Penetration Depth ◽  
Coherence Length ◽  
Symmetry Axis ◽  
Critical Magnetic Field ◽  
Ginzburg Landau ◽  
Iron Based Superconductors ◽  
Upper Critical Magnetic Field ◽  
Iron Based

This research work focuses on the theoretical investigation of the upper critical magnetic field,HC2; Ginzburg-Landau coherence length,ξGL(T); and Ginzburg-Landau penetration depth,λGL(T), for the two-band iron based superconductorsBaFe2(As1-xPx)2,NdO1-xFxFeAs, and LiFeAs. By employing the phenomenological Ginzburg-Landau (GL) equation for the two-band superconductorsBaFe2(As1-xPx)2,NdO1-xFxFeAs, and LiFeAs, we obtained expressions for the upper critical magnetic field,HC2; GL coherence length,ξGL; and GL penetration depth,λGL, as a function of temperature and the angular dependency of upper critical magnetic field. By using the experimental values in the obtained expressions, phase diagrams of the upper critical magnetic field parallel,HC2∥c, and perpendicular,HC2⊥c, to the symmetry axis (c-direction) versus temperature are plotted. We also plotted the phase diagrams of the upper critical magnetic field,HC2versus the angleθ. Similarly, the phase diagrams of the GL coherence length,ξGL, and GL penetration depth,λGL, parallel and perpendicular to the symmetry axis versus temperature are drawn for the superconductors mentioned above. Our findings are in agreement with experimental observations.

scholarly journals Restoration of superconductivity in high magnetic fields in UTe2

2020 ◽  
Vol 34 (32) ◽  
pp. 2030007
Author(s):  
Andrei G. Lebed
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Superconducting State ◽  
Critical Magnetic Field ◽  
High Magnetic Fields ◽  
Two Dimensional ◽  
Upper Critical Magnetic Field ◽  
Reentrant Superconductivity ◽  
Theoretical Results ◽  
General Method

It was theoretically predicted more than 20 years ago [A. G. Lebed and K. Yamaji, Phys. Rev. Lett. 80, 2697 (1998)], that a triplet quasi-two-dimensional (Q2D) superconductor could restore its superconducting state in parallel magnetic fields, which are higher than its upper critical magnetic field, [Formula: see text]. It is very likely that, recently, such phenomenon has been experimentally discovered in the Q2D superconductor UTe2 by Nicholas Butch, Sheng Ran, and their colleagues and has been confirmed by Japanese–French team. We review our previous theoretical results using such a general method that it describes the reentrant superconductivity in the abovementioned compound and will hopefully describes the similar phenomena, which can be discovered in other Q2D superconductors.

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